This invention relates to blankets for curing concrete and the like, and more particularly to a lightweight concrete cure blanket.
One of the usual requirements in producing quality concrete is the proper manipulation of the concrete during curing. Curing not only increases the strength of concrete and its structural value, but proper curing during the curing period is mandatory for the production of water-tight and durable concrete. During the concrete curing process, chemical changes occur in the presence of water which ensures that the hardened concrete will be water-tight and durable over time, resulting in a stable and sturdy cured physical structure. These chemical changes occur over a considerable period of time requiring that the concrete be kept wet after it has set during the curing period. However, one problem is that the heat radiating from the concrete during the curing process evaporates the moisture in the concrete, thereby inhibiting the chemical hardening process and compromising the strength and durability of the cured concrete.
It is therefore necessary to contain the heat and moisture in the concrete long enough to permit the curing process to be sufficiently completed. Not surprisingly, the need for heat and moisture retention increases during cold weather applications. With decreasing temperatures, the need for increased thermal retention requires the use of additional layers of insulation, resulting in concrete cure blankets of greater thickness which are heavy and cumbersome to use. It would be advantageous to have a lightweight multilayer moisture-impervious heat reflective concrete cure blanket that is capable of providing enhanced thermal resistance without a corresponding increase in the thickness or weight of the blanket.
Conventional moisture-impervious concrete cure blankets use combination foam, Fiberglass, air filled bubble layers, and like materials as insulative layers. However, such blankets are susceptive to accidental rips, and in the event the interior insulation gets wet, the insulating quality of the insulation material is reduced. Another method to keep the curing concrete moist utilizes frequent sprinklings, but this approach is labor intensive and expensive. To promote curing, horizontal concrete surfaces are usually covered by sand, canvas or burlap to maintain the desired dampness. But irregular and/or vertical concrete surfaces cannot be adequately covered and have to be sprinkled periodically to maintain the required damp condition. Concrete cure blankets are typically used to cover water-wetted concrete to extend the duration of the damp condition for as long as possible. It would be advantageous in the art to have a lightweight and durable, multilayer, moisture-impervious, heat reflective concrete cure blanket having enhanced thermal resistance and which is also universal in use in that it can be used for curing either horizontal or vertical concrete structures regardless of size. It would also be advantageous to provide a lightweight and durable heat reflective concrete cure blanket which is inexpensive to produce, and may be discarded after use.
One prior art attempt to solve these problems is taught by U.S. Pat. No. 5,549,956 to Handwerker, the present inventor, titled “Heat Reflective Blanket” which is directed to a flexible, multilayer heat reflective blanket containing at least one interior heat reflective, (i.e., metal foil) layer, and at least one interior insulative layer. It has been discovered that a heat reflective concrete cure blanket configured to include an insulative layer as well as a heat reflective layer improves and enhances the effectiveness of the blanket, thereby making the blanket more efficient for its intended use. While the blanket disclosed in U.S. Pat. No. 5,549,956 satisfactorily enhances the concrete curing process; the configuration of this type of concrete cure blanket is somewhat expensive. It would be an advantage in the art if a lightweight, multilayer, moisture-impervious, heat reflective concrete cure blanket could be manufactured inexpensively, and yet also be durable and long-lasting.
Another approach to solve the above problems is taught by U.S. Pat. No. 4,485,137 to White titled “Concrete Curing Blanket” which is directed to a lightweight summer concrete cure blanket which improves water retention in the curing concrete irrespective of the surface irregularities present in the concrete. The cure blanket provides for effective water wicking or capillary wetting action characteristics across the entire blanket. The concrete cure blanket can be easily sealed with adjacent blankets to provide continuous coverage of a large area of curing concrete without tearing the blankets. The White concrete cure blanket has a nonporous surface layer of a low density polyethylene that is heat sealed as a coating upon a batting layer of a porous, resilient, non-woven, needle-punched, synthetic fabric such as polypropylene or commercially available polymeric filament fabric. While having a porous exterior surface layer, the opaque surface layer of this concrete cure blanket will block visible sunlight and UV radiation. However, this concrete cure blanket is not suitable for winter concrete curing utilization, since the prior art blanket cannot reflect the heat radiating from the curing concrete, and the evaporation of moisture from the curing concrete remains a continuous operational problem thereby requiring rewetting of the curing concrete from time to time as needed during the curing period. It would be an advantage in the art if a lightweight, multilayer, moisture-impervious heat reflective concrete cure blanket were available to the construction industry.
Yet another attempt to provide an efficient concrete curing blanket is shown in U.S. Pat. No. 5,855,978, to Handwerker, the present inventor, which describes a concrete cure blanket having top and bottom moisture-impervious outer layers, at least one heat insulative layer disposed between the top and bottom layers, the bottom outer layer composed of a woven material with a heat reflective material applied to the lower surface of the woven material. The disclosed concrete cure blanket of this prior art patent includes a woven polyethylene layer having added reflective material applied to the outer facing surface of the lower outer layer. This differs from the present invention, which does not incorporate a woven polyethylene layer and an additional reflective layer, which provides a blanket of less weight and manufacturing costs than shown in Handwerker U.S. Pat. No. 5,855,978.
The initial costs associated with the production of various concrete cure blankets disclosed in the prior art make such blankets expensive to acquire. It would be an advantage in the art if a lightweight, multilayer, moisture-impervious, heat reflective concrete cure blanket could be manufactured relatively inexpensively and easy to maintain, or even disposable, by utilizing long-lasting thermoplastic films formed into at least one bubble type structure having a relatively small thickness and weight, in combination with reflective materials.
The present invention overcomes these and other problems that are inherent in existing multilayer and other concrete cure blankets.